Cell nucleus

In cell biology, the nucleus (pl. nuclei; frae Laitin [nucleus] or [nuculeus] , meanin kernel or seed) is a membrane-enclosed organelle foond in eukaryotic cells. Eukaryotes uisually hae a single nucleus, but a few cell teeps, sic as mammalian reid bluid cells, hae na nuclei, an a few ithers hae mony. Human skeletal muscle cells hae mair nor ane nucleus, as dae eukaryotes lik fungi.

HeLa cells steened for nuclear DNA wi the Blue Hoechst dye. The central an richtmaist cell are in interphase, sicweys thair entire nuclei are labeled. On the left, a cell is gaeing throu mitosis an its DNA haes condensed.

Cell nuclei conteen maist o the cell's genetic material, organised as multiple lang linear DNA molecules in complex wi a muckle variety o proteins, sic as histones, tae form chromosomes. The genes within these chromosomes are the cell's nuclear genome an are structurt in sic a wey tae promote cell function. The nucleus mainteens the integrity o genes an controls the activities o the cell bi regulatin gene expression—the nucleus is, tharefore, the control centre o the cell. The main structurs makkin up the nucleus are the nuclear envelope, a dooble membrane that encloses the entire organelle an isolates its contents frae the cellular cytoplasm, an the nuclear matrix (that includes the nuclear lamina), a network within the nucleus that adds mechanical support, muckle lik the cytoskeleton, that supports the cell as a hale.

Acause the nuclear membrane is impermeable tae muckle molecules, nuclear pores are required tae regulate nuclear transport o molecules athort the envelope. The pores cross baith nuclear membranes, providin a channel throu that muckler molecules maun be actively transportit bi cairier proteins while allouin free muivement o smaw molecules an ions. Muivement o muckle molecules sic as proteins an RNA throu the pores is required for baith gene expression an the maintenance o chromosomes. Awtho the interior o the nucleus daes nae conteen ony membrane-boond sub compartments, its contents are nae uniform, an a nummer o sub-nuclear bouks exeest, made up o unique proteins, RNA molecules, an pairteecular pairts o the chromosomes. The best-kent o thir is the nucleolus, that is mainly involved in the assemmly o ribosomes. Efter bein produced in the nucleolus, ribosomes are exportit tae the cytoplasm whaur thay translate mRNA.